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Riva Greenberg

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Why Can't Meters Tell Me My Blood Sugar?

Posted: 06/26/2012 12:37 pm

The 72nd American Diabetes Association scientific session took place a few weeks ago.

More than 16,000 medical professionals, scientists, researchers, pharma industry representatives and some well-versed patients attended.

The exhibition hall boasted one of the largest displays of new-to-market, and coming-to-market devices, technologies and other products to make managing diabetes easier, safer and more precise.

But I, and you, are still checking our blood sugar on a glucose meter that's allowed to be anywhere within 20 percent of the laboratory standard 95 percent of the time.

What that means is when my meter says my blood sugar is 145 mg/dl (8 mmol/l) it might be -- or, given the up to plus or minus 20 percent, it might be 113 mg/dl (6.2 mmol/l) or 173 mg/dl (9.6 mmol/l), or anywhere in between.

In 2010 the FDA wrote, "Glucose meters are increasingly being used to achieve tight glycemic control despite the fact that these devices have not been approved for this use." The article goes on to say that patients at home and those in clinical settings are using glucose meters that have not been approved as safe and effective.

Nearly 26 million people have diabetes in the U.S. Nearly 80 million have pre-diabetes. While they don't all use meters, meter accuracy is not limited to a small, exceptional group. Since within 10 years most people with pre-diabetes will go on to get Type 2 diabetes, meter accuracy will grow to affect up to a third of the nation.

So while manufacturers keep adding bells and whistles to meters, and we're on the launch pad for an artificial pancreas -- where accuracy will be even more critical -- why don't I have a meter that gives me an accurate reading of my blood sugar?

Think about it: would you buy a scale that's 20 percent off? Your 145 pounds on the scale might really be 113, 127, 165 or 173 pounds, or anywhere in between. Would you drive a car whose speedometer gave the speed up to plus or minus 20 miles per hour? How useful would a watch be that was sometimes too fast and sometimes too slow and you didn't know when it was which?

Six to 10 times a day when I check my blood sugar, I'm making a decision to either eat more calories -- eating sugar if my blood sugar's too low, to bring it up -- or take more insulin if my blood sugar's too high, to bring it down. And that, my friend, can be a life-threatening action if I'm basing it on faulty numbers.

To minimize some worry, you should know that the governing body, the International Organization for Standardization (ISO), states that the rate of allowable accuracy on your meter must be within 15 percent of the laboratory standard when your blood sugar is lower than 75 mg/dl. But still...

Variance Meter to Meter
Not only do we not know how off the mark our meter readings are, testing your numbers on one meter next to another will drive you mad. Different meters give you different results, almost a different range of results.

Last month at a pre-launch press meeting at Sanofi, I got an iBGStar meter. I've been using Bayer's ContourUSB meter for the last two or three years, so I immediately checked my blood sugar on both meters. For the sake of these lists being difficult to read, here are the results in the U.S. mg/dl value:

2012-06-25-firsttest.png

I checked twice more over the next day and in each case my ContourUSB showed I was 20-25 points lower than the iBGStar.

Fascinated, I wanted to check on more meters. I had a VerioIQ and Freestyle Lite meter at home and ordered a Freestyle Freedom Lite meter.

Here are my results from eight checks of my blood sugar at the same moment, same finger, using the same drop of blood. (I only checked on Freestyle Freedom Lite twice because it arrived toward the end of my testing.)

2012-06-25-Screenshot20120625at11.44.24AM.png

Here's another thing that happened when I checked, and then checked again a minute later:

2012-06-25-moretests.png

So if you check twice in a row on the same meter you won't necessarily get the same result.

I've been told the only way to know if your meter is accurate is to check your blood sugar on your meter when you're having it drawn for a lab test and compare when the lab test result comes back. I did this two weeks ago. The number on my ContourUSB was 115 mg/dl (6.3 mmol/l). The lab came back with 139 mg/dl (7.7 mmol/l).

While I titled this post "Why Can't Meters Tell Me My Blood Sugar?" I plan to do a second post on "Why Meters Can't Tell Me My Blood Sugar" if that's the case. I want to find out what is at the root of meter readings and disparities and what manufacturers are doing about it.

For now, I've been told the reason for accuracy distortion is largely the interplay between the strip and the meter. Plus a host of other variables like the calibration of the meter, dirt on the meter or strip, what's in your blood from medications you may be taking, what's on your fingers from what you last ate and environmental conditions like climate and altitude.

Here's my plea to the FDA, government, pharma and health insurance companies -- with all the new gizmos and cool designed products, which I applaud, let's also get our priorities straight. When 1 in 20 people with diabetes die from low blood sugar, why are we dragging our feet on getting our meters accurate? What are we waiting for?

So what's your experience? Have you checked on different meters?

Do you think one meter is more accurate than the others? Why?

Have you compared checking your blood sugar on your meter with the hospital standard lab draw?

Have you switched meters and then found you have to get used to new numbers?

On a personal note I want to say to those of us who live with diabetes and constantly feel we are judged by our numbers -- our health care providers judge us, our family may judge us and we judge ourselves -- we really don't know what our numbers are. Plus no matter how hard we work at keeping our blood sugar in our target range, there are other forces at work -- stress, illness, the 20 percent margin of error the FDA allows food manufacturers on food nutrition labels -- that we can't always have the numbers we'd like. Let's try to remember that each time we check our blood sugar and when we do get meter accuracy.

Riva speaks to patients and health care providers about flourishing with diabetes and is the author of "50 Diabetes Myths That Can Ruin Your Life and the 50 Diabetes Truths That Can Save It" and "The ABC's Of Loving Yourself With Diabetes." She is finishing her third book, "Diabetes Dos & How-Tos due out this fall. Visit her website DiabetesStories.com.

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11:26 AM on 07/02/2012
I've been having issues with highs and lows. So, yesterday, I decided to check a finger on each hand with the same meter-one immediately right after the other. Hands had been thoroughly washed and dried. There was an 18 point difference!! This is insane!! But I am so glad to know that this is an issue with the meters and not with my body. Thank you!!
08:31 PM on 06/30/2012
Thank you for raising an important issue with blood glucose meters. Like you and other commenters, I too have conducted similar experiments! I am surprised there isn't an independent organization or university that has conducted and published a comparison of recently FDA approved and older meters for consistency and accuracy across a wide range of glucose values.
10:45 AM on 06/28/2012
Thanks for the article, while I haven't compared meters, I have had dangerous instances of having a high blood sugar; then while preparing a dose of insulin, I decide to check it once more. The second reading would be significantly lower.
05:20 PM on 06/27/2012
As someone familiar with the FDA standard for error (which references the 20% error mentioned) for blood glucose meters, it may require some clarification about what the standard allows for readings below 75mg/dL
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Riva Greenberg
10:07 PM on 06/27/2012
Thanks Carl. For anyone who missed it, it says in the article "To minimize some worry, you should know that the governing body, the International Organization for Standardization (ISO), states that the rate of allowable accuracy on your meter must be within 15 percent of the laboratory standard when your blood sugar is lower than 75 mg/dl. But still..."
10:27 AM on 06/28/2012
Below, 75mg It's not 15%, it's 15mg/dL... Even worse. But still..
10:15 AM on 06/27/2012
It's been my pet peeve for years! It's almost impossible to have really tight control. The difference between a 4.5 and a 3.8 mmol/l is a decision making nightmare! I'm either low or not. Best out of 3? Sometimes that's what I do. Shouldn't have to. Yet a lab blood test is accurate? Not necessarily - there are slight differences between labs, especially with A1C.

I applaud the technology that has been developed over the last 30 years, but meters are lagging way behind. There are one or two more accurate than others (I have a drawer full of them), but is that really good enough?

We yell from Australia about our meters, but apparently not loudly enough. Maybe you'll have some better luck from over there. It's high time we had something more accurate!
09:51 PM on 06/26/2012
Great article Riva. I too did testing on other meters, before and after I did my lab work. I too use the contour and my readings were off on each machine by sometimes more then 20%. What is the answer? Thank you for helping me realize I am not crazy! I will continue to follow you on this subject and many more. You do a great job in keeping us all posted. Thank you !!! Love you Doreen A1C Champion Family Living With Diabetes
12:53 PM on 06/26/2012
Spot on and thank you for writing this. We have several different meters in the house (freestyle, freestyle lite, contour,novamax nova link, novamax plus, and one ultra link) and have done the same thing, especially when my daughter is sick. The contour is consistently lower than all the others, the freestyle lite most consistent with back to back testing, and massive strip error issues with novamax and one touch. My daughter and I both want to achieve tight control with her blood sugars, her endo expects that. So, how crazy is it to read that BG meters aren't FDA approved towards that end, or to know that there is no push toward or acceptance of CGM as a tool in the accepted standard of care? FDA - this is an issue that *needs* to be addressed. I don't care about all the bells and whistles if we can't get better meter accuracy. I a trying to prepare my daughter to enter the world ready and able to manage her diabetes independently, she and other PWDs deserve better, more accurate tools. Frankly, you can't tell me the technology and ability to improve doesn't already exist.